Michael, thanks so much for the photos, that's a lot easier for me than having to deal with the museum.
I have this little slideshow of the hackbut, and if this is not adequate I will sit down and try to figure out how to post photos individually on this forum; of course I have separate url's for each one.
This hackbut was ordered by Ulrich von Schellenberg; you must be familiar with him because you like the Katzbalger, and Ulrich's sword in the KHM is one one of the finest I can imagine. I have a photo of it if anyone needs it but I have a feeling you all know that one.
The barrel is all I have, it weighs 36 lbs, is 36.75 inches long, and the bore measures 20.3mm, or 0.8 inches.
The barrel is bronze with a few iron inclusions including the chaplets for the core and one iron ring underneath (broken off.)
Decorations include flames, trefoils, and other unknown geometric shapes in patterns or rings around the barrel. The coat of arms is that of von Schellenberg.
Above the coat of arms are the letters which at first appear to be "I V R" but I am told by historians should be read as "J U R." I have thought of several possibilities for these letters but have not arrived on one that is foolproof yet.
Here's the slideshow, just mouse over the grid to see the photos.
There are several photos of a small round mark which appears to be struck, on the flash pan, and I thought it might be some kind of proof mark or maker's mark, but it is very indistinct, some simple figure, perhaps a bird in flight, in a circle?
Any insight you can give on this is most welcome.